Conventional hypodermic needle covers comprise small diameter tubular coverings with an opening at one end for receiving a needle. These needle cover are placed over the needle when hypodermic syringes are first assembled to keep them sterile. The same needle cover may also be used to cover the needle after the hypodermic needle has been used. It has long been a problem that persons inserting needles into the needle covers accidentally miss the needle cover opening and stick themselves with the needle. This is a serious problem because a number of serious diseases including hepatitis and AIDS are known to be spread in this way. Thus, it is important for persons using hypodermic needles not only to avoid direct contact with the needle, but also for them to avoid being in close proximity to an unsterile used needle.
In response to these problems, some efforts have been made to develop safety shields for hypodermic needles. These include U.S. Pat. Nos. 4,654,054, 4,573,975 and 4,623,336. The structures disclosed in these references provide some protection over conventional needle covers by means of new needle cover designs incorporating various kinds of shields. However, due in part to the complexity and cost of these special needle covers, they have not been widely employed. In addition, these shields, when inserted on an unused hypodermic syringe, make the total syringe package excessively bulky.
One partial solution is to use a sheild which attaches to a conventional standard needle cover. In this way, the cost of the shield is minimized because existing low cost, mass-produced needle covers may still be used with the shield. Also, if the shield is attached to the needle cover only after the syringe has been used, the problem of adding bulk to the unused hypodermic package would be eliminated. One example of such a structure is found in U.S. Pat. No. 4,559,042. However, a number of problems still are present with the type of shield disclosed in this, as well as other patents. First, while most shields provide some protection against accidental sticking, there is still the possibility of a needle slipping off the shield during insertion. This can occur because if the needle misses the central opening of the needle cover and strikes the shield on one side, the resulting of-axis torque is likely to cause the needle cover to tilt in the user's hand. During the attempted insertion, this tilting can result in the needle slipping off the shield where it may strike the user's fingers, hands or arms that are not directly behind the shield. While simply making the shield much larger is one possible solution, as a practical matter, the diameter of the shield must be kept to a reasonably small size. In addition, a number of previous shields are flexible and this flexibility may also contribute to the needle slipping off the edge of the shield.
An additional problem with prior needle shields that are designed to be used with conventional needle covers, is that the shield can be removed from the needle cover. Removability opens the possibility of medical personnel reusing the same shield with a different needle cover. Because the shield may have had contact with the first needle and also because in the process of removing the shield the needle cover may be removed and the needle exposed, there is a chance of infection when the needle shield is removed from the needle cover.
The present invention improves upon previous needle shields by providing a needle shield that can be attached to a standard needle cover. The present invention also provides a needle shield with a means for locking the needle cover onto it so that the needle shield cannot be removed. The shield is rigid and also provides a rim for preventing the needle from sliding off the edge of the shield during insertion.
Accordingly, it is a general object of the present invention to provide a new and improved hypodermic needle shield. It is a more particular object of the present invention to provide a hypodermic needle shield which is simple, low-cost and can be used with a conventional needle cover. It is yet another object of the present invention to provide a hypodermic needle shield that cannot be removed from the standard needle cover and reused. It is still a further object of the present invention to provide a hyprodermic needle shield that is rigid, small enough to be of practical use, yet effective in preventing the needle from slipping off the edge of the shield when the needle strikes the shield on one side during an attempted insertion of the needle into the needle cover.
Additional objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying claims.